[Organizers] matchmaking

Booking-related: How do you manage the (sometimes) delicate task of matching callers and bands? For example, what if you book a caller, but then find out the already-booked band doesn't want to work with that person? Besides the strategy of first booking a caller (or band) then asking for confidential suggestions on what bands (or callers) they'd like to work with (or not), how does an organizer handle this sort of "I won't play in the same sandbox as Susie" syndrome? What special or particular circumstances would affect your response and/or would guide you to a particular solution? - 2014 NEFFA session ** Please RETAIN SUBJECT LINE in all replies! Especially IF YOU GET THE DIGEST! ***